Oxidovanadium(V) Anchored to Silanol-Functionalized Polyoxotungstates: Molecular Models for Single-Site Silica-Supported Vanadium Catalysts

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• 作者：Geoffroy Guillemot ; Edoardo Matricardi ; Lise-Marie Chamoreau ; Ren茅 Thouvenot ; Anna Proust
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：December 4, 2015
• 年：2015
• 卷：5
• 期：12
• 页码：7415-7423
• 全文大小：448K
• ISSN：2155-5435

文摘

The metalation of two different types of silanol-decorated polyoxotungstates, [XW₉O_34鈥?i>x(^tBuSiOH)₃]^{3鈥?/sup> (X = P, x = 0; X = Sb, x = 1) and [PW₁₀O₃₆(tBuSiOH)₂]3鈥?/sup>, by Cl₃VO or (iPrO)₃VO has been achieved. The characterization of the resulting oxidovanadium(V) complexes [XW₉O_34鈥?i>x(tBuSiO)₃VO]3鈥?/sup> (X = P, 3; X = Sb, 3鈥?/b>) and [PW₁₀O₃₆(tBuSiO)₂VO(iPrO)]3鈥?/sup> (4) has been fully detailed, including X-ray analysis. These compounds are present in monomeric forms and therefore represent original molecular models for tris-grafted and bis-grafted isolated (V鈺怬)3+ species dispersed onto silica. Their ability as precatalysts for the epoxidation of cyclic olefins and allylic alcohols with tert-butyl hydroperoxide (TBHP) has been studied. The results suggested that a confined tris-grafted species, such as 3 or 3鈥?/b>, does not act as an efficient catalyst whereas a more labile bis-grafted species, such as 4, does. To gain a better understanding, we have assessed their suitability for ligand exchange with alcohols and TBHP and performed reaction progress kinetic analysis by monitoring the epoxidation of 3-methyl-2-buten-1-ol by 1H and 51V nuclear magnetic resonance.}